The present invention relates to a circuit breaker, more particularly to a circuit breaker which displays the cause of the disconnection of a conductor connecting the source and the load in a power distribution system and is not affected by the excessive voltage.
Wiring circuit interrupters and current leakage circuit interrupters are commonly used devices for protecting people and property from fire and dangerous electrical faults. Wiring circuit interrupters are used to protect power lines. The circuit interrupters are tripped by the bending of an internal bimetal when excessive current passing through a circuit breaker is converted to heat. The circuit interrupters are also tripped causing the bimetal to heat up and bend when an electric tool or other metallic object on the load shorts the power line and high current is passed through instantaneously. This causes the electric device to be interrupted by the inner magnet of the circuit interrupter.
There are three cases where an incident like fire may happen during power transmission. The three cases are incidents by an arc fault, a ground fault and an overload, respectively.
The overload occurs when the excessive current flows from the source to the load, which is usually caused when many electronic devices are used simultaneously. The overload often occurs when air conditioners are used in summer. If excessive current flows, the bimetal emits the heat and the inner bimetal is bent, which results in disconnection of the conductor connecting the source and the load.
The ground fault occurs if there are metallic materials near the conductor of which a coating is stripped off. If the ground fault occurs, there may occur leakage current, which results in electric shock.
The causes of an arc fault are numerous. For example, it may be caused by overuse, excessive currents or lightning strikes, loose connection or excessive mechanical damage to insulation and wires. According to the Consumer Product Safety Commission (CPSC), it was estimated that 40% of the fires in 1997 were due to arc faults. The National Electric Code (NEC) requires AFCI installation in all the residential buildings beginning in January 2002.
The overload and the ground faults are temporary. Therefore, users may reconnect the conductor although the conductor is disconnected by the overload or the ground fault.
However, as the arc faults are caused by defects of the conductor, users should not reconnect the conductor until the fundamental defect of the conductor is resolved.
Therefore it is helpful for users to display the cause of the disconnection of the conductor, which allows users to determine whether to reconnect the conductor.
The circuit breaker of the prior art have displayed the state of the circuit breaker only mechanically by changing the state of a switch or changing the color expressed in a certain outer portion of the circuit breaker.
However, above mechanical display methods fail to display the cause of disconnection and users can""t see the state of the circuit breaker at night if the display is made mechanically.
Therefore, it is necessary to display the state of the circuit electronically. However, there has been difficulty to display the state of the circuit electronically as power can""t be provided if the circuit breaker disconnects the conductor connecting the source and the load.
Moreover, most countries require that the circuit breaker should overcome regular voltage which is relatively high. For example, the United States of America requires that the circuit breaker should overcome 1240V. As most of circuit elements cannot overcome a voltage over 1000V, it is still more difficult to display the state of the circuit breaker and the cause of the disconnection electronically.
In order to resolve the above-described problems in the conventional circuit breaker, the present invention intends to provide a circuit breaker which is able to display the state of a circuit breaker electronically.
Another purpose of the present invention is to provide a circuit breaker which enables users to determine whether to reconnect the circuit, by displaying the cause of disconnection electronically.
Another purpose of the present invention is to provide a circuit breaker which is able to display the state of the circuit breaker although the circuit is disconnected, for example on overload.
Another purpose of the present invention is to provide a circuit breaker which is able to display the state of the circuit breaker although a high voltage is applied to the circuit breaker.
In order to above-mentioned objective, a circuit breaker according to the invention comprises at least one of an arc fault detector, a ground fault detector, and an overload detector and disconnects a conductor coupling a source and a load if at least one of the arc fault detector, the ground fault detector and the overload detector generates a trip signal. The circuit breaker further comprises means for displaying the state of the circuit breaker and the cause of the disconnection if the conductor is disconnected by the trip signal generated from at least one of the arc fault detector, the ground fault detector and the overload detector, and means for resetting the means for displaying if the disconnected conductor is reconnected, wherein the means for displaying is driven by an independent source.
The means for displaying may comprise at least one of an arc fault display means displaying the state of arc fault responsive to the trip signal from the arc fault detector, a ground fault display means displaying the state of ground fault responsive to the trip signal from the ground fault detector, and an overload display means displaying the state of overload responsive to the trip signal form the overload detector.
The arc fault display means, the ground fault display means and the overload display means may comprise a silicon controlled rectifier, respectively, in order to form a closed circuit with the independent source responsive to the trip signal.
The arc fault display means, the ground fault display means and the overload display means may comprise an NPN transistor and a PNP transistor respectively in order to form closed circuit with the independent source responsive to the trip signal, wherein the trip signal is provided to the base of the NPN transistor, and the collector of the NPN transistor is coupled to the base of the PNP transistor.
The arc fault display means, the ground fault display means and the overload display means may comprise a light emitting diode which is driven responsive to the trip signal.
The reset means may comprise a bipolar junction transistor.
The reset means may comprise a field effect transistor.
The trip signal may be provided to a base of the bipolar junction transistor, an emitter of the bipolar junction transistor is grounded, and a collector of the bipolar junction transistor is coupled to the independent source.
The means for displaying comprises a microprocessor, a digital display and at least one of a first level detector, a second level detector and a third level detector, wherein the first level detector coupled to the arc fault detector generates an output signal in case of receiving the trip signal from the arc fault detector, the second level detector coupled to the ground fault detector generating an output signal in case of receiving the trip signal from the ground fault detector, the third level detector coupled to the overload detector generating an output signal in case of receiving the trip signal from the overload detector. The microprocessor receives the output signal from one of the first level detector, the second level detector and the third level detector, determines state of the conductor and the cause of the disconnection and generates a control signal according to the result of the determination. The digital display displaying the state of the conductor and the cause of disconnection according to the control signal from the microprocessor.
The independent source may be a battery.
The independent source may be a storage battery.